Calculate exactly how much spray foam insulation you need in board feet, the required thickness, and estimated spray foam insulation cost. Compare open cell vs closed cell spray foam side by side.
Choose open cell or closed cell spray foam, then enter your dimensions.
Spray foam insulation is a high-performance insulation material that is sprayed as a liquid and expands into a solid foam, filling every gap, crack, and cavity. Unlike blown in or batt insulation, spray foam creates both an insulation layer and an air barrier in one application, making it one of the most effective insulation options available.
There are two types of spray foam insulation:
Open cell spray foam has an R-value of R-3.5 to R-3.7 per inch. It is softer, lighter, and more affordable. Open cell foam is excellent for interior walls, attics (at the roofline), and soundproofing. It allows some moisture to pass through, which can be an advantage in certain climate zones.
Closed cell spray foam insulation has an R-value of R-5.5 to R-6.5 per inch — the highest of any common insulation material. Closed cell spray foam is rigid, acts as a vapor barrier, and even adds structural strength to walls. It is the best choice for crawl spaces, basements, exterior walls, and any area where moisture resistance is critical. The closed cell spray foam R-value makes it possible to achieve high insulation levels in thin wall cavities.
Our spray foam insulation calculator helps you determine the exact board feet needed, required thickness, and estimated spray foam insulation cost for your project.
Our spray foam calculator uses a simple process to estimate your needs. Here is how to calculate spray foam insulation step by step:
Measure the length and width of the area you want to insulate. Multiply them to get total square footage.
Spray foam is measured in board feet. One board foot equals 1 square foot of coverage at 1 inch thick. Divide your target R-value by the R-value per inch of your chosen foam type:
For example, to achieve R-19 with closed cell spray foam (R-6.0/inch): 19 ÷ 6.0 = 3.2 inches. With open cell (R-3.6/inch): 19 ÷ 3.6 = 5.3 inches.
Multiply your square footage by the required thickness to get total board feet:
For a 1,000 sq ft area at R-19 with closed cell: 1,000 × 3.2 = 3,200 board feet.
The spray foam insulation cost per square foot varies by foam type. Multiply your square footage by the cost per square foot to get your spray foam insulation cost estimate:
| Foam Type | R-Value/Inch | Material Cost/Sq Ft | Installed Cost/Sq Ft |
|---|---|---|---|
| Open Cell | R-3.5 to R-3.7 | $1.00 – $2.00 | $1.50 – $3.00 |
| Closed Cell | R-5.5 to R-6.5 | $1.50 – $3.50 | $2.50 – $5.00 |
The spray foam cost per square foot includes the foam material at the required thickness. How much does spray foam insulation cost for a typical project? For a 1,000 sq ft attic with open cell at R-30, expect $1,000-$2,000 for materials or $1,500-$3,000 installed. For closed cell spray foam cost on the same area at R-19, expect $1,500-$3,500 materials or $2,500-$5,000 installed.
Spray foam insulation is the best choice in these scenarios:
Understanding spray foam insulation cost helps you budget for your project. Here is a complete breakdown of spray foam insulation cost per square foot:
| Project | Open Cell (Material) | Open Cell (Installed) | Closed Cell (Material) | Closed Cell (Installed) |
|---|---|---|---|---|
| 500 sq ft Wall | $500 – $1,000 | $750 – $1,500 | $750 – $1,750 | $1,250 – $2,500 |
| 1,000 sq ft Attic | $1,000 – $2,000 | $1,500 – $3,000 | $1,500 – $3,500 | $2,500 – $5,000 |
| 300 sq ft Crawl Space | $300 – $600 | $450 – $900 | $450 – $1,050 | $750 – $1,500 |
| 80 sq ft Rim Joists | $80 – $160 | $120 – $240 | $120 – $280 | $200 – $400 |
The average cost of spray foam insulation falls between $1.50 and $4.00 per square foot installed, depending on foam type and project complexity. Spray foam insulation cost per sq ft is higher than blown in or batt insulation, but the superior air sealing and R-value per inch often make it the most cost-effective long-term choice. How much does spray foam cost compared to other options? While the upfront cost of spray foam insulation is 2-3× higher than blown in, the energy savings typically pay back the difference within 3-5 years.
For an accurate estimate of how much is spray foam insulation for your specific project, use our spray foam insulation cost calculator above. It factors in your exact dimensions, foam type, and desired R-value to give you a personalized spray foam insulation cost estimator result.
Choosing between open cell and closed cell spray foam insulation is one of the most important decisions for your project. Here is a detailed comparison:
| Feature | Open Cell | Closed Cell |
|---|---|---|
| R-Value per Inch | R-3.5 to R-3.7 | R-5.5 to R-6.5 |
| Density | 0.5 lb/cu ft (light) | 2.0 lb/cu ft (dense) |
| Moisture Barrier | No (vapor permeable) | Yes (vapor barrier) |
| Structural Strength | No | Yes (adds racking strength) |
| Air Sealing | Excellent | Excellent |
| Sound Reduction | Excellent | Good |
| Material Cost/Sq Ft | $1.00 – $2.00 | $1.50 – $3.50 |
| Installed Cost/Sq Ft | $1.50 – $3.00 | $2.50 – $5.00 |
| Best For | Interior walls, attic rooflines, soundproofing | Crawl spaces, basements, exterior walls, moisture-prone areas |
| DIY Friendly | Small areas only | Small areas only |
Closed cell foam insulation cost is higher, but it delivers nearly double the R-value per inch, acts as a moisture barrier, and adds structural strength. For most homeowners, the choice comes down to location: use open cell for interior applications where moisture is not a concern, and closed cell spray foam for any area exposed to moisture or where maximum R-value in minimal thickness is needed.
DIY spray foam insulation kits are available for small projects, but there are important limitations to understand before you start.
DIY spray foam kits work well for rim joists (the most common DIY spray foam project), small crawl space sections, gap and crack sealing around windows and doors, and small wall sections under 200 sq ft. Do it yourself spray foam kit options range from $300-$600 and cover 200-600 board feet.
Large attic projects, full wall installations, and any project over 600 sq ft should be done by professionals. Spray foam requires precise temperature control (the chemicals must be at 70-80°F), correct mixing ratios, and proper application technique. Poor application can result in off-gassing, poor adhesion, and insulation that needs to be removed and redone — costing more than professional installation would have.
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